Am-413a/g military tube compressor

[Johnblue]

Long time no post. Haven’t had a bench to work on for a while, but I do now   Been going through my stuff and trying to pick off the low hanging fruit that’s been in storage for a while. 

I’ve searched high and low but can’t find a schematic. Luckily this puppy looks pristine inside and out and inside there isn’t an electrolytic in sight, all domino style caps.  Except for 1 bathtub style and the big filter caps.

Have you guys ever seen internally tied can style capacitors? I’m trying to figure out why one of the big 40uf power caps isn’t reading anything.  Before input the new caps in, the empty pin wasnt reading anything either.

Strange markings on the can, and the absolute 000 reading makes think maybe this first can was internally tied.

Also, the caps are rated 300v and the voltages are right about 300 across the board makes me think maybe the van

Also confusing is there’s a 6aq5 in line with the 000 cap acting as a regulator or something.

Does this marking on the can say that it’s internally tied?

 

[pucho812]

from the photo on the can it looks like a typical can capacitor, each cap has it's own Positive lead down to a pin, all the negative leads tie together to a pin and the can. it has a resistor marking going to ground so not sure what that is about. I suspect you have a dead 40uF/300V cap.  you can probablly find a replacement for an arm and a leg  or you can rebuild the can cap for much cheaper.

 

[Johnblue]

from the photo on the can it looks like a typical can capacitor, each cap has it's own Positive lead down to a pin, all the negative leads tie together to a pin and the can. it has a resistor marking going to ground so not sure what that is about. I suspect you have a dead 40uF/300V cap.  you can probablly find a replacement for an arm and a leg  or you can rebuild the can cap for much cheaper.

Actually, I already replaced the caps with new individuals.

First I removed the cans from the octal sockets. Then I fired up the transformer to test the voltages unloaded. I was surprised that only 2 of 3 of the pins were reading power 205vdc.  The last one read 000 ... with the caps removed.

Then I figured... okay, let’s install the 3 individual new caps. And same thing. The power went up to about 295vdc but that  last cap still isn’t receiving any power it reads 000

never really seen that type of drawing on a can before, and yeah that resistor symbol threw me off too... I was thinking... is this a  special military can?... and if the caps were internally tied in series it would solve my problem... haha wishful thinking.

The cap that is 000 is connected to a 6aq5 that’s acting as a regulator Or something, it’s really early in the circuit.

 

[Ricardus]

It can't hurt to email the guys over at Hayseed Hamfest and send them that pic and see what they know about that type of can.

I needed a replacement can cap for a NOS Heathkit tube amp I have and they made me a new one and were very helpful.

 

[emrr]

I take the dotted line resistor to indicate external components for expected use, is that what you're asking?  Otherwise looks like a standard multisection can.  I know I've seen that before, possibly on that same limiter.  Which is an odd bird. 

 

[Conviction]

The cap that is 000 is connected to a 6aq5 that’s acting as a regulator Or something, it’s really early in the circuit.

I would guess the 6AQ5 is the output tube, pushing those ~2 watts or whatever the unit is capable of. Look what it's connected to (probably the output transformer). It's physically close to to the optx too. I kinda doubt one of the 12AT7's drives the output. A 12AU7 would make more sense.

Ps: the schematic is really nowhere to be found. I just browsed through all those military docs out there.  :-\ Lots of descriptive data though.